A lithium-ion rechargeable battery (hereinafter referred to as lithium-ion battery), which is an ideal rechargeable battery replacing the traditional battery and the Ni—H rechargeable battery, Li-ion batteries are advantageous in their large energy density, fast chargeable/dischargeable characteristics, longer cycle life, low self-discharge, harmless and no memory effect. However, known lithium-ion battery has a relative high output voltage, and the output voltage varies according to different positive electrode systems. Commercial available lithium-ion batteries have nominal voltages ranging from 3.2V to 3.8V, and with a development of lithium-ion battery technology, the lithium-ion battery may have an even higher nominal voltage. Obviously, lithium-ion batteries cannot be used as direct substitutes for universal batteries with a nominal voltage of 1.5V or Ni—H rechargeable batteries with a nominal voltage of 1.2V.
Although lithium-ion battery has better charging/discharging characteristics, it has problems of poor overcharging/overdischarging toleration and poor charging overheat/discharging overheat toleration. If failing to control the charging/discharging properly, the lithium-ion battery may be ageing rapidly and damaged, or even may cause fire or explosion. Accordingly, a charging/discharging operation of the lithium-ion battery has to be controlled strictly according to the charging/discharging technical specifications of the lithium-ion battery.
Currently known lithium-ion battery structure package processes include mainly the following four types: i) a negative electrode outer housing lithium-ion battery package constituted by connecting the negative electrode current collector with the outer housing (typically, a steel outer housing package is employed); ii) a positive electrode outer housing lithium-ion battery package constituted by connecting the positive electrode current collector with the outer housing (typically, an aluminum outer housing package is employed); iii) a quasi-insulated outer housing lithium-ion battery package employing a soft packaging (typically, an aluminum-plastic composite film material packaging is employed); and iv) an insulated outer housing lithium-ion battery package having an outer housing constituted by an insulation packaging material (typically, a polypropylene and polyethylene outer housing package is employed).
Since uses of universal primary battery and Ni—H rechargeable battery have long history and have been standardized, methods for detecting low power of the battery using its output voltage have been developed in many universal battery application fields. For example, in electronic devices such as digital cameras, MP3, MP4, electronic smart locks, electronic instruments and the like, determination of battery low power is performed by detecting real time output voltage of the battery.
In addition, PCs, tablet computers, cell phones are highly popularized, and the rechargeable batteries use the USB interface of the computer and normal lithium-ion battery charging adapter as charging power sources, which may reduce acquisition cost and save social resources.
To solve the above problems, a patent, which number is 201110219892.0 about entitled with “rechargeable battery constituted by employing lithium-ion battery and control method” was published by the Chinese SIPO, in which the lithium-ion battery and the discharge control circuit are integrally packaged to constitute a universal rechargeable battery. However, rechargeable battery has few disadvantageous in the following aspects.
I. The rechargeable battery does not include lithium-ion battery charging control and charging overheat protection therein.
Since the rechargeable battery does not include lithium-ion battery charging control and charging overheat protection circuit therein, a diode is required during charging to isolate a charging circuit and a discharging circuit, and a dedicated external charging device having a lithium-ion battery charging control circuit and a temperature sensing circuit is necessary for charging. Accordingly, there exists following technical defects: i) during the charging, the forward voltage drop of the diode varies according to the differences of the operating current and temperature, thereby lowering accuracy of the charging control circuit to detect the lithium-ion battery and control the charging. An undercharge problem of the lithium-ion battery may occur when the diode has a relative higher forward voltage drop, and an overcharge problem of the lithium-ion battery may occur when the diode has a relative lower forward voltage drop, thereby lowering the charging and safety characteristics of the lithium-ion battery; ii) since the charging loop is connected with an isolation diode, the charging input voltage of the rechargeable battery is raised, and since the known lithium-cobalt lithium-ion battery has an upper threshold charging voltage up to 4.35V which may increase in the future, the undercharge problem of the lithium-ion battery may still exist in the case where the charging input voltage is at a lower limit and the forward voltage drop of the isolation diode is at an upper limit, even if schottky devices having lower forward voltage drop are employed when the battery is charged using a known universal lithium-ion battery charging adaptor or a USB interface of the computer having a nominal voltage of 5V±0.25V. Such a problem may be solved by employing a boosting circuit in the external charging device, however, this may cause problems of increasing cost, decreasing efficiency and reliability and the like of the charging device; and iii) the external temperature sensing circuit can only detect the temperature of the lithium-ion battery indirectly through outer packaging housing or the electrodes of the rechargeable battery, thereby lowering the accuracy of sensing the temperature of the lithium-ion battery during the charging and leading to problems of decreasing cycle life and safety due to charging overheat of the lithium-ion battery in the rechargeable battery.
II. The rechargeable battery does not include discharging overheat protection of the lithium-ion battery.
The rechargeable battery does not include lithium-ion battery temperature sensing and control circuit therein, such that the rechargeable battery does not have an overheat protection function during discharging process of the lithium-ion battery. Accordingly, there is a risk for the lithium-ion battery to work at a temperature over its upper threshold operating temperature when the rechargeable battery is discharged at a high discharging rate in a hot environment, thereby leading to problems of decreasing cycle life and safety of the lithium-ion battery.
III. A charging/discharging controller has complex structure and assembling process.
A circuit connection between a negative electrode of the charging/discharging controller and the packaging housing of the rechargeable battery employs a radial elastic clamping connection structural design. During the assembling of the rechargeable battery, an elastic negative electrode is required to be pushed radially to a predetermined position before the charging/discharging controller is able to be pushed into the packaging housing of the rechargeable battery. In addition, the elastic negative electrode is a moveable part with a structure occupying a relative larger inner space inside the charging/discharging controller, causing it difficult to seal the charging/discharging controller. Accordingly, the charging/discharging controller has a relative larger volume, complex and difficult manufacturing process, and it is difficult to realize an automatic mass production or the waterproof sealing thereof. Therefore, there exist problems of low power capacity, high producing cost, and possible circuit failure after getting wet in the rechargeable battery.